1. Field of Invention
The present application relates generally to medicine and veterinary practice, and, more particularly, methods and apparatus useful for assessing the level of fertility in mammalian females.
2. Background of the Invention
Methods and devices for assessing the level of a woman's, or female mammal's, fertility are important for primarily two reasons: contraception and, conversely, improving the likelihood of conception.
Contraceptive use in the United States is virtually universal among women of reproductive age: 98% of all women who ever had intercourse had used at least one contraceptive method in a 2002 survey (W D Mosher et al., “Use of Contraception and Use of Family Planning Services in the U.S.: 1982-2002”, Advance Data, 350:1-36, Dec. 10, 2004, Center for Disease Control (CDC)). The CDC statistics show a high rate of experience with non-chemical and non-barrier methods of contraception. In 2002 the percentage of women 15-44 years of age who have ever had sexual intercourse and who have ever used calendar rhythm was 13.9-16.6%, periodic abstinence/natural family planning was 1.9%-4.7%, and withdrawal was 47.2-59.7% (WD Mosher et al., Advance Data 350:1-36, Dec. 10, 2004, CDC). These data suggest that there is an interest in more “natural” methods of family planning. Fertility experts feel there is a need for “safer, more effective, and more user-friendly contraceptives.” (V F Strauss and M. Kafrissen, “Waiting for the second coming”, Nature 432: 43-45, 2004).
The other issue of family planning—improving the rate of pregnancy—is not addressed by hormonal or barrier contraception. Sexual intercourse is unlikely to result in conception unless it occurs during the 6-day fertile interval ending on the day of ovulation (D B Dunson et al., Human Reproduction 14:1835-1839, 1999; A J Wilcox et al., NEJM 333:1517-1521, 1995). A problem with fertility is defined as a year of unprotected coitus without conception. This affects 10-15% of couples of reproductive age, and is largely due to improperly timed attempts at conception. Thus, a family planning method that could be used to determine a woman's level of fertility, and thereby increase the probability of pregnancy, would be extremely useful.
Over the past several years there has been much interest in developing methods to predict and detect the time of ovulation and measure the level of fertility throughout the human menstrual cycle. For various health, religious, and philosophic reasons there is a great interest in natural methods of birth control which utilize biologic indicators of fertility to define an interval of sexual abstinence (G Freundl et al., Gynaekologe, 31:398-409, 1998; The European Natural Family Planning Study Groups, Adv Contraception 15:69-83, 1999).
One such method of using biological indicators to assess female fertility, described in U.S. Patent Application #20050171454, employs analysis of a urinary metabolite of estrogen (estrone-3-glucuronide) and luteinizing hormone (LH). One of the primary drawbacks of this method is practicality, as this test is expensive and requires considerable reagents. Additional impracticability, and inaccuracy, may abound in that the levels of urinary estrone-3-glucuronide may be variably connected with the level of fertility depending on the quality of cervical-vaginal secretions. Thus the biological indicator employed in that test may be a derivative, and a step removed, from the primary indicator of cervical-vaginal secretion quality. Other methods of measuring various hormones, such as progesterone, have similar issues of cost, reliability and accuracy.
Many of the other natural methods of family planning in current use (e.g., Billings Method) depend on indicators such as the texture and sensations of cervical mucus and cervical-vaginal secretions to predict the fertile phase of the cycle (J J Billings, The Ovulation Method Manual, Family of Americas Foundation, The Liturgical Press Collegeville, Minn., 1994). These methods are individualistic and subjective, and thus lack quantifiable and objective data for determining the level of a female's fertility.
Some female fertility assessment methods attempt to quantify the various qualities of the cervical mucus, based on the strong correlation between the quality of this fluid and the fertility of a female. Some of the these methods include using a refractomeric device to measure the refractive index of cervical mucus (U.S. Pat. No. 6,149,591), or using acoustic waves to measure the viscosity of cervical mucus (U.S. Pat. No. 4,691,714). Both of these methods again have problems of consistency and accuracy. Additionally, and importantly, both of these methods are impractical for personal use, as it is extremely difficult for women to obtain pure cervical mucus on their own.
The volume of cervical-vaginal secretions has also been employed as a biological indicator of female fertility. As described in U.S. Pat. No. 4,534,362, a Volumetric Vaginal Aspirator has been developed to allow women to take and read the volume of a daily sample of their cervical-vaginal secretions, and observe the timing of a volume peak that occurred approximately simultaneously with the peak in serum estradiol that precedes ovulation—thus predicting fertility. However, tests have shown that this volumetric analysis was able to predict fertility consistently in only a small proportion of women (A M Flynn et al., Human Reproduction 12: 1826-1931). Additionally, many women may not obtain sufficient cervical-vaginal fluid during the fertile period to register a significant enough change indicative of ovulation. Thus, volumetric analysis of cervical-vaginal fluids is also hampered by relatively low sample volumes (˜0.2 ml. at volume peak) in some women.
Other devices have attempted to measure the electrical resistance of vaginal fluid. However, again it appears that the measurement phenomena are not always demonstrably reliable.